Category: Challenger Mission (Page 8 of 37)

This past weekend Challenger crossed the 1000 km milestone on the trans-atlantic crossing from Brazil to South Africa.

RU 29 has completed the first 1000 km of the mission

Now at 1041 km into the mission, 29 is now roughly 1/6 along the projected path passing by Tristan de Cunha to Cape Town.

RU29 Crossing the South Atlantic

Looking to the forecasted currents, the two models are both showing that Challenger is flying down the eastern side of a cold core eddy which combined with the new way point from Friday has led to an extra ~3km per surfacing.  Despite the increased distance, Challenger is continuing to show a slight overall flux to the north through its calculation of depth average currents.

Copernicus Averaged Currents August 03

RTOFS Averaged Currents August 03

Moving at this pace, we will continue to have Challenger pursue the current way point for another 2-3 days before we move the way point back east to account for the edge of the eddy we are currently taking advantage of

Force, Wind, Sea & Honor

As we head into the weekend, there is a new way point waiting to be picked up by Challenger the next time she calls in.  In preparation for the next surfacing, we have moved the way point to 30˚ South, 32˚ West in an attempt to catch the southerly current shown in both the Copernicus and RTOFS forecast models as seen below:

Copernicus Averaged Currents July 31, 2015

RTOFS Averaged Currents July 31 2015

This current should propel us to the south east over the next few days during which we hope to get a good idea on if the forecasted current are matching the gliders flight path so we can use the information to make the next way point move early on next week.

Antonio has also provided us with the salinity fields from the Copernicus forecast this week which gives us an ever better picture of the eddy field 29 is on the cusp of entering

Copernicus Salinity field forecast for 540m depth

There are two things that are really cool about the eddy field we are entering, the first being that from here on out the eddies we are encountering are part of the influx into the Atlantic from the indian ocean (see below) and the second is that the cold eddy to the south has remained relatively stationary over the seamounts in that region, similar to the cabo frio eddy along the coast of Brazil that Challenger encountered on the Ascension – Brazil trek.

Copernicus Sea Surface Height Forecast July 31

Force Wind Sea & Honor

Through the weekend Challenger continued to make good time as she flies to the south east with the distant shores of Cape Town in her sights.

As we start off the week, the discussion turns to picking the next waypoint.  The path we want to stick to falls along the orange line shown in the image above, stepping down the eddies that span the South Atlantic in a pattern very close to the pattern of 1˚ to the South, 3˚ to the East.

Copernicus Averaged Currents July 20, 2015

Looking to the Copernicus forecasted currents, we will have another few days or so of the currents pushing to the North until we will start to find the currents Challenger will be able to ride off to the east as she snakes through the eddies.

Force Wind Sea & Honor

Today we have one of those rare occurrences where not only do the models match up quite well, but in a pretty favorable fashion.  Both forecasts seen below (RTOFS in green in the first image and Copernicus in yellow in the second)  show a warm eddy and cold eddy combination about 300km to our south east that will be aiming for over the next week.  They also agree that if we keep our heading a bit to the south along our approach we should find more favorable currents along the way.  With our current waypoint, Challenger should progress somewhat along the white line shown in the images if the forecasts hold true.

RTOFS Currents for July 16. Average of 300, 600, 1000m

Copernicus Currents for July 16. Average of 300, 600, 1000m

Tomorrow morning after our pre weekend discussion we will set a new way point further out to the south east to pursue through the weekend as we try and hit the sweet spot between those two eddies.

Force Wind Sea & Honor

RU29 flew straight east over Friday and Saturday until it passed north of the seamount.  With the strong northward currents, much of RU29’s flight has been eastward so far. Early Sunday morning the waypoint was changed back to Southeast, based on the depth average currents plots from the U.S. and European models. We are currently heading in the direction shown by the orange line. And we again are in international waters.  The yellow lines mark the EEZ limit for Brazil.  Hopefully the next EEZ we enter is South Africa’s.

Zooming out to the long view, below is the South Atlantic Basin.  RU29’s trip around the basin is divided into 3 legs. Leg 1 (blue) was from Cape Town, South Africa to Ascension Island in 2013.  Leg 2 (green) was Ascension to Ubatuba, Brazil in 2014.  Leg 3 (red) is one potential flightpath back to Cape Town via Tristan da Cunha. We’ll keep this red line up as a reference.  We are currently flying along the orange line.  Total great circle  distance to Cape Town from the present location is 5,600 km.  Assuming a strong speed of 25 km/day, its about 7.5 months to cover this distance. Again assuming all goes well, that gets us to Cape Town about March 2016 at the earliest.  We are leaving tropical Brazil during the southern hemisphere winter.  As we fly southeast, we will transition into southern hemisphere summer, hopefully arriving Cape Town as their summer is ending.

Now two weeks into our mission, the team has been looking forward to which path we will take in the coming months on 29s trek to South Africa.  Our dear friend Antonio laid out four possible paths we can take:

Each of the paths stretch between 5500 and 6000km which will last around 245-280 days. The differences in the path options appear during the first 1/2 of the mission upon reaching Tristan de Cunah.  This mission will be the longest of 29’s so far and the small secluded UK archipelago is the only port available to us along the way.

Later, after crossing to the north of the EEZ of Tristan de Cunha, the paths merge as piloting shifts to jumping from eddy to eddy as they pass around the Cape of Good Hope, leading Challenger back to Cape Town.

Antonio also provided us with some nice 3D imagery of the bathymetry.  Featured in the image above, is a region of sea mounts and volcanos that are jutting up from the seabed. Going forward, we plan to pass to the north of the mountains just ahead of us before snaking our way to the south.

Looking to the forecasted currents, we have an interesting conflict to our south east.  In the image below, black vectors represent the copernicus currents at 300m while the white currents are RTOFS. 

Both forecasts show an eddy signature to the south east, however copernicus defines it as a clockwise cold core eddy while RTOFS shows it as a counterclockwise warm core eddy.

Both forecasts however show a prominent southern current a head which we plan on catching over the next few days.

Force Wind Sea &  Honor

Compare today’s currents (below) with those in yesterday’s blog entry.

Yesterday we had currents to the north for a few hundred kilometers, followed by a longer region of currents to the south.  Today we have the opposite.

We’ll need to look closer at our forecast tools.

RU29 has a cluster of seamounts due east of it.  Over the weekend we tried to pass to the south, but our trajectory says no.  Strong currents to the north prevented us from heading on a southeast track. We checked the current forecasts for an alternative plan.

Below is the RTOFS forecast for today.  Strong currents to the north for the next few hundred kilometers.  Followed by strong currents to the south.

We are planning to change the waypoint to due east.  Combined with the current to the north, the glider trajectory will be northeast, and we will pass north of the seamount cluster.  We’ll then continue into the southward flowing currents, and let the ocean take us back south.

Now at sea for just over a week, Challenger is continuing to fly strong as ever.  Just over 250km into the roughly 6000 km mission, the glider has been covering between 27-35 km/day while using a minimalist 2.16 amp hours/day.  At this rate, we should be able to squeeze about 350 days out of the battery packs as 29 weaves her way across the South Atlantic.

 With this afternoons surfacing, Challenger popped up roughly 5 km from Brazil’s exclusive economic zone, so early tomorrow when she next surfaces, 29 will once again be in international waters; the first of many mile stones for the new trans-atlantic mission.

Copernicus currents at 300m

For the past few days, 29 has been riding a nice tail current as she made her way down the eastern edge of a cold core eddy.  However looking at the latest surfacings, the currents reported by the gliders calculations have been showing the slowing of the tail current as we pass off from one eddy to the next as seen in the image above of the Copernicus forecasted currents for 300m depth.  In order to change the angle Challenger is flying at to catch the more favorable currents eastward, I moved the waypoint a few degrees to the north.  With this adjusted flight path, she will now take a more favorable path to the north of the cold eddy to the east as we fly over the seamounts that lie ahead.  Below is a path we hope to fly outlined in red as Challenger snakes her way through the terrain.

Force Wind Sea & Honor

Challenger is now 3 days into her mission to connect the shores of Brazil and South Africa as she completes the circumnavigation of the South Atlantic. This will be the longest leg of the mission, however our team is confident we are up to the task.

RTOFS Model of Surface Currents and Sea Surface Height

Based on our ocean model road maps and the bathymetry that lies ahead, we hope to fly a path similar to what is outlined below with the red line.  The figure below shows 29’s position as of this afternoon overlayed with the Copernicus (formerly myocean) ocean forecast data for roughly 350m depth.  The recent forecasts are showing the signature of a large counter-clockwise rotating warm eddy to the south west producing the strong northward push the glider is reporting in her calculations of the currents.  The way point is currently just to the North of the island of Tristan de Cunha well off to the South East, but combined with the eddy’s flux to the north-north-west the glider is flying nearly due east.

Copernicus Currents from ~350m depth

Looking ahead, Antonio provided us with a neat plot of the northward component of the currents of the South Atlantic.  In the figure below, red signifies northward components of the current while blue represents a southern flux.  There is an overwhelming overall flux to the north, however we will be doing our best to snake our way through the patches of blue and white as we aim for the southern edges of the counter-clockwise warm eddies and northern edges of the cyclonic cold eddies of the South Atlantic

Northward Flux of the South Atlantic at 450m June 26

We also must keep an eye on the bathymetry that lies ahead as there are some significant sea mount formations that we will encounter as we fly to the south east.  In the map below of the sea floor,  the black line depicts roughly the 1300m isobath.

Bathymetry of the South Atlantic

Finally, the following are pictures taken off the coast of Brazil earlier this week while Dr. Marcelo Dottori and his team deployed Challenger

Force Wind Sea & Honor